Different proposals for single-axis hinge devices prepared to allow lifting the hood in the event of hitting a pedestrian are known today. In the scope of the invention, single-axis hinges refer to hinges in which the hood is connected to the hinge device in an articulated manner about a single rotating shaft. These devices differ from other hinge proposals in which the movement of the hood is connected to the device by means of a type of articulated parallelogram, such that the hood follows a compound motion during maneuvers for closing or opening it.
Some single-axis hinge devices comprise articulated structures that allow lifting the rotating shaft of the hood in the event of hitting a pedestrian. There are known proposals using pyrotechnic devices triggered based on a signal generated by detectors which detect hitting a pedestrian and exert a thrust force on a component of the articulated structure, causing it to change from a compact shape to an extended shape, lifting the rotating shaft of the hood from the position it adopted in the compact shape. Logically, these devices have means for assuring that the device adopts the compact shape during normal operation, i.e., as long as an accident triggering the pyrotechnic device does not occur. Furthermore, for safety reasons, the articulated structure is prevented from moving in a direction that may cause the lowering of the rotating shaft of the hood.
The means which detect hitting a pedestrian and generate the trigger signal for triggering the pyrotechnic device are calibrated so that said signal is generated when a pedestrian is hit within pre-established speed ranges that may be indicated by different safety regulations with a minimum speed threshold value. At present, this means that the trigger signal is not produced if the vehicle speed is less than a value that varies between 20 and 25 km/h according to manufacturers. In these circumstances, the hinge device does not provide any active or passive response in the event of hitting a pedestrian, pedestrians being subject to the deformation that the metal plate of the hood may experience in the impact area. Nevertheless, this deformation is heavily conditioned by the points where the hood is anchored or secured to the vehicle, and said points are not disabled in the event of hitting a pedestrian at a speed below the aforementioned minimum threshold value and are formed by the articulated attachments with the hinge devices in the rear part of the hood and with the locking device of the hood in the front part thereof.
An objective of the invention is a hinge device capable of responding in the event of a situation of hitting a pedestrian when no signal whatsoever triggering the pyrotechnic device is generated, for example, when a pedestrian is hit at low speeds.
Another objective of the invention is a hinge device allowing controlled movement and deformation of the hood in the event of hitting a pedestrian and when the pyrotechnic device or equivalent element is not actuated.
Another objective of the invention is a hinge device the behavior of which varies depending on the location of the impact on the hood.
It is of interest that this hinge device is compatible with hood systems using pneumatic pistons for cooperating in the operations of opening the hood which tend to arrange the hood in an open position.
A hinge complying with the described objectives while at the same time being constructively simple and easy to adjust is also of interest.